The present invention relates to a drive apparatus of foldable blind, screen or the like used in car windows or the like.
Conventionally, a blind apparatus as disclosed in Japanese Unexamined Utility Model Publication No. 58-161033 has been known. This conventional apparatus comprises, as shown in FIG. 4 and FIG. 5, a hollow cylindrical drum 1, a blind 2 foldably wound on the drum 1, a bottom bar 3 attached to the leading end of the blind 2, a brace 4 fitted and fixed to a wall 5 of eaves or the like for rotatably supporting the drum 1, and an arm 6 for coupling the bottom bar 3 and the brace 4. The arm 6 is foldable in the blind spreading direction, and is designed to applying an extruding force in the blind spreading direction to the bottom bar 3 of the blind 2 by a spring not shown. That is, the arm 6 has an extrusion mechanism for applying a stretching force to the blind 2.
The drum 1 is rotatably supported on fixed shafts 7, 8 fixed to the braces 4 by way of bearings 9, 10. Inside of the drum 1, as shown in FIG. 5, a motor 15 with a reduction gear as the rotating force source is accommodated in a state fixed on the fixed shaft 7 and not contacting with the drum inner wall 1a. 
A rotary shaft 12 of the motor 15 is mounted on the drum 1 through a one-way clutch 13. The one-way clutch 13 functions to transmit the rotating force to the drum 1 when the rotary shaft 12 rotates in the blind take-up direction.
The fixed shaft 7 is hollow, and lead wires 14 of the motor 15 are taken out through the inside of the fixed shaft 7.
In this configuration, explaining the spreading and take-up operation of the blind 2 by the drum 1, first, as indicated by double dot chain line in FIG. 4, the blind 2 is taken up on the drum 1, and when the motor 15 is unlocked and rotated in the blind spreading direction, the blind 2 is expanded to the spread final end by the pushing force of the arm 6 while the expanding speed is being regulated at the rotating speed of the motor 15 by the one-way clutch 13. When the blind 2 is sent out to the specified position, the drum 1 receives a rotation stopping force from a rotation stopping mechanism (not shown) of the drum 1, and the motor 15 is decoupled from the drum 1 by the one-way clutch 13, so that the rotary shaft 12 is set in idling state. As a result, only by setting the expanding rotation time of the motor 15 slightly longer, reverse winding or loosening of the blind 2 can be securely prevented. On the other hand, in the spread state of the blind 2, when the motor 15 is rotated in the blind take-up direction, the rotary shaft 12 is coupled with the drum 1 through the one-way clutch 13, and the drum 1 is rotated by the rotating force of the rotary shaft 12, so that the blind 2 can be taken up.
In the conventional blind apparatus, however, switch or other detecting mechanism was needed in order to detect the upper limit position and lower limit position of the blind 2. In addition, the rotation stopping mechanism of the drum 1 and lock mechanism of the drum 1 were needed after spreading and after take-up of the blind 2. Further, after taking up the blind 2, in order to eliminate effects of inertia of rotation of the motor 15, mechanisms were necessary for coupling the internal rotor of the motor 15 and the rotary shaft by frictional clutch or magnetic clutch, and allowing the rotary shaft to slip in an overloaded state, and the configuration of the blind apparatus was much complicated, and an inexpensive product could not be presented.
Conventionally, moreover, since the motor 15 is disposed in the drum 1, only spur gears, helical gears or planetary gears can be used as the reduction gears, and the operating noise was loud.
The present invention is directed to solve the above-mentioned problem, and it is hence an object of the present invention to provide an inexpensive and less noisy blind apparatus having a simple structure.
It is another object of the invention to present a blind apparatus capable of preventing looseness of the blind after spreading the blind, extending the service life of the motor mechanical parts, and unlocking immediately if a foreign matter is caught in the blind, and being further advantageous in the aspect of safety and much lowered in operating sound level.
In order to achieve the above-mentioned object, according to one aspect of the present invention, a blind apparatus comprising a drum on which a blind is wound, a motor for rotating the drum in a blind spreading direction or a blind take-up direction in order to expand or take up the blind, an extrusion mechanism having a foldable arm for thrusting the leading end of the blind thereby a spring force in the blind spreading direction, and a one-way clutch for transmitting the rotating force of the motor to the drum when the drum rotates in the blind take-up direction, further comprises: a stopper for stopping move of the arm near the blind spreading end position, and a detecting circuit for detecting a motor lock current when taking up the blind, wherein a stopping position in the blind spreading direction is detected by the arm position regulation by the stopper, and a stopping position in the blind take-up direction is detected by the motor lock current by the detecting circuit.
In the apparatus of the invention, when spreading the blind, the upper limit position of the blind can be detected only by stopping the blind at the spreading end position by a stopper. On the other hand, when taking up the blind, the lower limit position of the blind can be detected by detecting a motor lock current. As a result, the upper and lower limit detecting mechanism (switch and the like) used in the conventional blind can be omitted, and the drum rotation stopping mechanism and the drum lock mechanism after the spreading and take-up operation of the blind are not necessary. Hence, an inexpensive blind apparatus can be presented in a simple structure.
According to a feature of the present invention, a control circuit stops after driving the motor in the spreading direction when spreading the blind for a specified time required for the blind to reach the spreading end position, and then drives the motor for a short time in the blind take-up direction, then, looseness of the blind caused by not applying stretching force to the blind with the arm position regulation can be prevented.
According to a further feature of the present invention, a control circuit stops the motor after detecting the motor lock current by the detecting circuit in the blind take-up operation, and then drives the motor for a short time in the blind spreading direction, then, load applied to the motor can be removed, and hence the service life of motor mechanical parts can be extended, and the blind apparatus is extended in the service life.
According to a further feature of the present invention, a control circuit stops the motor when detecting the motor lock current by the detecting circuit at a blind take-up intermediate position, and then drives the motor for a short time in the blind spreading direction, and if a foreign matter is caught in while taking up the blind, the foreign matter can be removed easily. In particular, when a part of body of a person is caught in the blind, the blind reverse rotation mechanism is put in effect, and it is unlocked immediately, and it is also enhanced in the aspect of safety.
According to a further feature of the present invention, a reduction gear mechanism comprising a drive side worm and a driven side worm wheel is disposed between an output shaft of the motor and a rotary shaft of the drum, and a helix angle of gears of the worm and the worm wheel is set so that a direction of load applied in a thrust direction of the worm wheel from the drive side worm in the blind spreading operation may be identical with a direction of load applied in the thrust direction of the worm wheel from the arm through the rotary shaft of the drum, and in the spreading operation of the blind, the worm wheel always rotates while being pressed to one side in the thrust direction and jerkiness in the thrust direction is prevented, and the operating sound level is lowered in the spreading operation. As a reduction gear mechanism, by using a worm and the worm wheel having a self-locking function, effects of inertia of rotation of the motor can be eliminated, and the lock mechanism of drum after taking up the blind, and the frictional clutch or magnetic clutch inside the motor required in the prior art can be omitted, and moreover since by rotating the motor reversely after locked, the motor is unlocked so that the rotary shaft does not be slipped in overloaded state, and the slip arresting mechanism of the rotary shaft can be also omitted.